Reforming process



Feb. 28, 1956 M. TARNF'O LL REFORMING PROCESS Filed Sept. 5, 1952ATTORNEYS United States PatentO REFORMING PROCESS Morris Tampoll,Newark, N. J., assigner to The M. W. Kellogg Company, Jersey City, N.J., a corporation of Delaware Application September 5, 1952, Serial No.308,083

4 Claims. (Cl. 196-50) This invention relates to an improved reformingprocess, and more particularly pertains to a hydroforming process forproducing aviation gasoline of 100/ 130 grade, based on F-3 and F-4ratings.

Usually a finished aviation gasoline is not produced from a hydroformingoperation. The base stock which is necessary for the F-4 rating of theaviation gasoline is prepared by the hydroforming operation, and thisstock is generally blended with other hydrocarbon materials in order toobtain a finished product which also has the desired F-3 rating.Normally, a once-through hydroforming operation produces alsohydrocarbon material of 5 and 6 carbon atoms, but this material is notsatisfactory for use in blending with the base stock to obtain thedesired finished gasoline, because the F-3 rating thereof is notsutiiciently high to effect this purpose.

T lie catalysts which are generally used in the hydroforming processpossess isomerization properties, and so the lighter fractions producedin the operation can be repassed or recycled to improve the F-3 rating.The Cs fraction may be processed to isomerize n-hexane, and improve theblending value thereof, and hence, effect an improvement in the qualityof the iinished gasoline. However, the quantity of n-hexane whichremains unconverted after the recycle operation adversely influences therequired speciiication of the gasoline.

To attain the desired finished gasoline from a hydroforming operation itis found advantageous in the present invention to recycle along with theCs fraction, hydrocarbon material of tive carbon atoms. In the C5fraction there is present n-pentane, and this material is signifivcantlyhigher in F-B and F4 ratings than n-hexane, and so, the amount which maynot be converted to isopentane during the recycle step does notadversely influence the aviation gasoline specification as much as then-hexane. Furthermore, the recycling of the C5 fraction has the effectof lowering the concentration of n-hexane which might ultimately end inthe finished gasoline, and hence render such material less effective inlowering the F-3 gasoline rating. The production of aviation gasolinehaving D/130 rating from a hydroforming operation is quite unusual, andthus, this invention represents a maior advance in the production of'aviation gasoline.

By means of the present invention it is proposed preparing aviationgasoline by the method which comprises contacting naphtha with areforming catalyst under suitable conditions in a reforming zone,separating the C5- Cs fraction which is present in the product thusproduced, recycling part of the (I5-Cs fraction to the reforming zone,separating an aviation base stock from the remainder of the product, andcombining the base stock and the remainder of the Cs-Cs fraction as theproduct of the process.

The naphtha which is processed by means of this invention is derivedfrom any source, and it can be either straight run, cracked naphtha ormixtures of both. It is preferable, however, to employ a straight runnaphtha,

because the oletinic content is less and,theretore, better Mice aviationgasolines are produced. In general, the feed material containsanaphthene content of about 20 to` about 60% by volume, and thesenaphthenes include those having 5 and 6 carbon atoms in the ringstructure. Naphtha fractions containing large quantities of naphthenesare known to produce products which are exceptionally good as aviationbase stocks. The percentage of naphthene compounds in the feed materialis controlled by regulating the initial boiling point and the end pointof the naphthene material. In this regard, it is customary to employ afeed material having an initial boiling point of about to about 150 F.and an end point of about 280 to about 325 F. Such a material issuitable for the purposes of the present invention, however, in viewthat it is necessary to employ recycle stock comprised of lighthydrocarbons having 5 and 6 carbon atoms, it is desirable to employ afeed material which contains these components. Accordingly, a preferredfeed material is one which has an initial boiling point of about toabout F. and an end point of about 290 to about 300 F. in order to haveincorporated therein a significant number of hydrocarbons having about 5to 6 carbon atoms in the molecule and little or none of those compoundshaving fewer carbon atoms. In this manner, the product produced from thereforming operation is certain to contain some hydrocarbons having 5 to6 carbon atoms which can be used for blending with the aviation basestock, which is a highly concentrated fraction containing aromaticcompounds.

This preferred feed material should be low in oleiinic content,generally, about 0 to about 5 mol per cent, based on the fresh feed. TheWatson characterization factor of the feed material can varyconsiderably, although those having a factor of about 11.0 to about 11.7are preferred, because they usually contain unusually large quantitiesof naphthenic compounds. The sulfur content in the feed material may beimportant from the standpoint of affecting the yield and quality of theproduct material which is produced. For the production of aviationgasoline, it is usually desirable to employ a feed material having about0.00 to about 0.20% by Weight of sulfur, although stocks containing moresulfur than indicated can be used with less satisfactory results.

As is to be expected, hydrocarbons having 5 and 6 carbon atoms in themolecule are produced in the reforming operation lby virtue of largemolecules in the feed material being cracked into products of lowermolecular weight. Under the conditions normally used for the reformingoperation, there is an insigniiicant amount of cracking of hydrocarbonmaterials having 5 and 6 carbon atoms in the molecule, however, suchcompounds tend to undergo isomerization, dehydrogenation, etc. Anyolefinic compounds which are produced by reason of cracking reactionsare generally isomerized under conditions which usually occur in thereforming operation. Consequently, the yield of olefinie material isgenerally in the range of about 0 to about 5 mol per cent based on theproduct material. With the exception of changing the straight chaincompounds having 5 and 6 carbon atoms to isomeric compounds and, in somecases, to aromatics through hydrocraeking reactions, little of thematerial is converted to lower molecular weight hydrocarbons. Therefore,when employing a feed material having compounds 'of 5 and 6 carbonatoms, it is to be expected that the product will contain compounds ofthe same number of carbon-atoms in greater quantity than in thoseoperations inwhich the yfeed material was substantially free of suchcompounds.

The product derived from the reforming operation is subjected to aseparation treatment in order to recover a fraction containingsubstantially all of the compounds having 5 and and 6 carbon atoms tothe molecule. For

the purposes of this specification, such compounds are designated as theCs-Cs fraction. Recycling of the Cs-Cs fraction is done in order toeffect further isomerization of the straight chain hydrocarbons,particularly n-pentane and n-hexane. N-hex'ane has a low F-3 and F-4rating; .whereas its isomers are significantly better in this regard. Ina oncethrough operation, the quantity of n-hexane which is found in theproduct is undesirably large and therefore it is dicult to obtain asatisfactory finished aviation gasoline. Hence, it is important toeither lower the concentration of n-hexane in the product material, orto convert it to a more useful compound, i. e., isohexane. Recycling theC5 fraction along with the Cs fraction accomplishes a two-fold purpose,viz., (l) lowering the concentration of n-hexane in the final product,and (2) diluting the n-hexane with a more desirable material, i. e.,n-pentane which can be converted to isopentane. Isopentane is especiallydesirable as an aviation gasoline component because the F-3 rating ishigher than most of the isomerized Cs hydrocarbons. Furthermore,n-pentane has a significantly higher F43 rating than n-hexane.Therefore, the concentration of n-hexane is lowered by means of addinghydrocarbons which are higher in F-3 ratings, i. e., those having 5carbon atoms, such as isopentane and n-pentane. Gern erally, inthereforming operation, the quantity of recycle employed is measured as therecycle ratio, which is defined as the ratio of the quantity of Cs-Csfraction which is recycled to the reforming zone to the quantity offresh Afeed which is charged to the process, on a volumetric basis.Accordingly, the recycle ratio generally used is about 0.5 to about3.011, preferably about 1.0 to about 2.0: l.

The aviationbase stock is the portion of the liquid product which ishighly concentratedin aromatic compounds containing at least sevencarbon atoms. This base stock serves as the material which furnishes therequired F-4 rating for the nished aviation gasoline. Usually, the basestock is separated from the total product as a material having aninitial boiling point above that which would include a significantamount of the hydrocarbons containing six carbon atoms, for example,about 180 to about 225 F. The end point of the base stock is selected onthe basis of eliminating substantially those aromatics having nine andmore carbon atoms in the molecule. Such heavy aromatics have a boilingrange which is too high according to specifications for satisfactory useas an aviation fuel. Normally, the C9 aromatics have acceptable F-4ratings and for this reason about 5-l0% by weight can be included withthe base stock. Consequently, the base stock has, in general, an endpoint of about 280 to about 325 F.

The catalyst employed for this process can be any suitable reformingcatalyst which possesses the properties of dehydrogenation,hydrogenation, isomerization and cyclization. Such a type of catalyst isone which is normally used for the reforming operation and includes, forexample, the oxide and/or sulfide of a group V or group Vl metal of theperiodic table as well as platinum and/ or palladium either alone orsupported on a carrier material. The carrier material used for thispurpose is, for example, alumina in the form of a gel or the activatedtype, silicaalumina, silica, silica-magnesia, kieselguhr, pumice,fullers earth, clays, etc. lt is generally desirable to add a smallamount of silica to the carrier material when employing alumina as aprimarysupport in order to increase its heat stability. In this respect,about 0.1 to about 12%, preferably about 2 to about 8% of silica isemployed for this purpose. Alumina is `generally regarded as a favoredsupport for the reforming reaction. The catalytic element or agent isemployed in varying amounts for the reforming reaction. Generally, thecatalytic agent is about 0.05 to about by weight, based on the totalcatalyst. In the case of using a catalytic agent which is a sulfide and/or oxide of a metal of groups V and VI of the periodic table, it ispreferred to employ about l to about 10% by Weight based on the totalcatalyst and this agent. On the other hand, when platinum and palladiumis employed as the catalytic agent, it is preferred to employ 0.1 toabout 5% by weight thereof, based on the total catalyst. Specificexamples of catalysts which are of use in the reforming operation aremolybdena on alumina, platinum on alumina, chromia on alumina, tungstenoxide on alumina, etc. lt is to be noted, however, that reformingoperations generaliy employ either a molybdenum oxide on aluminacatalyst, with or without being stabilized with silica, or platinum onalumina with or without silica being additionally present.

The reforming operation is generally conducted at an elevatedtemperature of about 850 to about 1050 F., preferably labout 900 toabout 975 F. At this elevated temperature, the pressure can be variedover a large range, namely, from about 25 to about 1000 p. s. i. g.,although more usually the range is about 50 to about 500 p. s. i. g. Thereforming operation is accomplished in the presence of hydrogen, eitherin the pure forni or a diluted stream having light hydrocarbons presenttherein. The quantity of hydrogen added to the process will determinewhether hydrogen is to be produced o'r consumed in the system. Thehigher hydrogen partial pressures tend to favor consumption of hydrogen,and therefore, in an operation involving a production of hydrogen, careshould be taken to control the hydrogen partial pressure in a rangewhere hydrogen is produced in quantities suiiicient to sustain theprocess. The hydrogen partial pressure can be at least about 25 p. s. i.a. and it can be raised to the point where hydrogen is consumed in ahydroforming operation. More usually, in a reforming operation, theamount of hydrogen supplied is determined on the basis of the cubic feetof hydrogen (measured at 60 F. and 760 mm.) which are charged to thereforming zone per barrel of total oil feed. (The barrel being equal to42 gallons.) Generally, for any type of reforming operation hydrogen canbe supplied to the process at the rate of 500 to about 20,000 standardcubic feet per barrel. ln a hydroforming operation, that is, wherehydrogen is produced, it is preferred to employ a hydrogen rate of about1500 to about 7500 SCFB. The hydrogen which is produced in the system isseparated from the remainder of the reaction product, howeverit usuallydoes contain light hydrocarbons, that is, primarily those having about 1to 3 carbon atoms in the molecule and some heavier compounds. This gasis recycled to the reforming zone, and it may contain at least 35% ofhydrogen, although more usually it contains about 45 to about 80% byvolume of hydrogen.

ln a xed and moving bed system, the 'severity of operation may bedetermined by the volumetric space Velocity, which is measured as thevolume of oil charged to the reforming zone, on an hour-ty basis, pervolume of catalyst which is present therein. In the operation forproducing aviation gasoline, the severity of the operation is generallyhigh, and therefore, the volumetric space velocity is in the range ofabout 0.1 to about 4.5, more usually, about 0.2 to about 2.0, preferablyabout 0.3 to about 1.0. In a moving ed system, the severity of theoperation may be determined by an additional factor, and that is, thecatalyst to oil ratio, on a weight basis. In general, the catalyst tooil ratio for a moving bed system is about 0.05 to about 3.011,preferably about 0.2 to about l.5:1, depending upon the catalyst used.The severity of the operation may be also measured by means of a weightspace velocity factor which is measured as the weight of oil charged tothe reaction zone, on an hourly basis, per weight of catalyst in thereaction zone. In general, the Weight space velocity for a moving andfixed bed system generally runs about 0.10 to about 4.0, more usually,about 0.1 to about 2.0, preferably about 0.1 to about 1.0, dependingupon the catalyst used.

`5 For the purpose of this invention, the process can be operated aseither a fixed or moving bed system. The fixed bed system can involve afluid or non-Huid catalyst, and it can include at least two vessels,whereby one vessel is processing oil and the other vessel is undergoingregeneration in order to revivify the temporarily deactivated catalyst.In this manner, there is a continuous flow of processing materials, andhence, greater quantities of product are obtained. More usually, incommercial practice, four vessels are employed in the system in order toincrease the capacity of operation. `Fora fixed bed system, the catalystemployed can be finely divided, granular, lump or pellets. In a movingbed system, the catalytic material can be granular or finely divided,however, the finely divided catalyst is utilized in order to operate bymeans of the fluid principle. In this regard, the linely dividedcatalyst has a particle size of about to about 250 microns, more usuallyabout 10 to about 100 microns. The processing materials are passedupwardly through a mass of finely divided catalyst at a superficiallinear gas velocity of about 0.1 to about 50 feet per second, moreusually about 0.5 to about 6 feet per second. For commercial operations,it is preferred to employ a superficial linear gas velocity of about 1to about 21/2 feet per second. At the latter velocities, a denselluidized mass of catalyst is obtained which is optimum for contactinggas and solid particles. In a moving bed system, separate vessels areemployed for the reaction and the regeneration,lso that catalyst isbeing circulated from one processingzone to another in a continuousmanner. The superficial linear gas velocities prevailing in all theprocessing zones fall within the range given above.

By reason of the reforming reaction, there is deposited on the catalystcarbonaceous material which causes temporary deactivation. In order torestore the catalyst activity, it is subjected to a treatment with anoxygencontaining gas, e. g., air, oxygen, diluted air containing about 1to about 10% by volume of oxygen, etc. The carbonaceous material isremoved from the catalyst through combustion at a temperature of about600 tol nitrogen, steam, light hydrocarbons, hydrogen, recycle gas, etc.Stripping serves to remove from the catalyst any hydrocarbon materialwhich is occluded and/or adsorbed thereby. Stripping is effected atessentially the same temperature which exists in the regeneration zoneor it can be higher or lower than the regeneration temperature,depending upon the type of operation required.

In order to more fully understand the present invention, reference willbe had to the accompanying drawing in which there is illustrated anoperation by which aviation gasoline was produced having a 100/ 130grade, based on F-3 and F4 ratings, respectively.

In the gure, fresh naphtha feed is fed from a source 5 at a rate of 252barrels per day (l barrel is equal to 42 gallons), and by means of apump 6 it is transported vto the top section of an absorber tower 7. Thetower v760y mm.) is discharged from the top of the absorber y40 at therate of about 79,400 cubic feet per hour.

v6 tower 7 through an overhead line 13. The gas discharged from the topof the absorber tower is passed to the fuel gas system which is notshown in the drawing. There is installed in the overhead line 13, apressure control valve 14 for the purpose ofv maintaining the desiredpressure in the absorber tower system. The fresh feed which is suppliedthrough line 5 has the following characteristics:

API gravity 64.2

IBP, F 108 5 154 Aromatics, vol. percent 16.0

Naphthenes, vol. percent 36.0

The fresh naphtha feed, laden with light hydrocarbon material, is mixedwith a recycle naphtha, supplied at the rate of 365 barrels per day,through a line 16 leading to the top of the feed surge drum. Thisrecycle naphtha has the following properties:

API gravity 74.5

IBP, F 88 5 100 10 104 20 108 30 119 40 127 50 136 60 142 70 145 80 16790 176 E. P 189 Any water which is present in the hydrocarbon materialis withdrawn from the bottom of the surge drum 1t) by means of a valvedline 18. The mixture of recycle naphtha and enriched fresh feed iswithdrawn from the surge drum 10 through a bottom line 19, and by meansof the pump 20 installed therein, it is transported through a heatexchanger 22 at the rate of 617 barrels per day. Prior to entering theheat exchanger 22, vthe temperature of the oil feed is F. and as aresult of being heated in the exchanger, the temperature is raised to430 F. Thereafter, the total feed is passed through a line 23 which isconnected to the convection coil 24 of a furnace 26. After passingthrough coil'24, the total feed is passed through coils 27 and 28 of thefurnace in succession, and then, it leaves the furnace by means of line30 at a temperature of 970 F.

kThe vaporized oil feed which leaves the furnace 26 passes first throughline 30, up to the junction with line 40 containing the heated recyclegas, following which the combined streams then enter line 33, in whichthere is valve 34 in an open position, for entry of the combined .feedmaterial and recycle gas into the upper section 36 of the reactionvessel 38. The reactor 38 is a cylindrical, vertical vessel in whichthere is supported pelleted molybdena-alumina catalyst containing 9% byweight of molybdena. This reactor yvessel contains 7 tons of catalyticmaterial for the reaction. The temperature in the reactor is such thatthe'average is about 935y F., and the inlet pressure of theenteringvfeed materials is about 277 p. s. i. g. The passage of reactantmaterials downwardly through the catalyst effects a pressure drop ofabout 7.1 p.s. i. g. Heated recycle gas containing. about 69% by volumeof hydrogen'is supplied through a line The a'rsaesa valve 41 in therecycle gas line 49 which branches from recycle gas line 40, ismaintained in a closed position during this phase of the operation. Thereaction product leaves the reactor vessel 38 and enters a section 42connected to the bottom thereof wherein the temperature is about 897 F.The reaction product then passes into a line 44, containing valve 45 inthe open position. This material then passes into a header 47 Themixture of recycle gas and reaction product passes into a line 50, andthence through heat exchanger 22, wherein the heat contained in thestream is indirectly transferred to the incoming feed material, which isfed to the furnace 26. The cooled recycle gas and reaction producthaving a resultant temperature of 3l0 F., passes into a line 52 beforeentering the cooler 53, wherein the ternperature is further decreased,prior t'o passing to a gas separator 55 through a line 56. In the gasseparator, the normal gaseous material under a pressure of 255 p. s. i.g. is separated from the liquid material. The liquid product is removedfrom the bottom of the gas separator through a line S8, and it istransported by means of pump 59 and line 60 to the product recoverysystem which will be discussed in more detail hereinafter. Thetemperature of the liquid product in the gas separator is 86 F. Anywater which is present in the separator 55 is removed from the bottomthereof through a valved line 62.

The normally gaseous product material is removed from the top -of thegas separator 55 through a line 65, and thence, it is divided so that aportion is passed through line 12 in which there is located a controlvalve 66 for the purpose of maintaining the pressure in the gasseparator. The other portion of the normally gaseous product materialflows througha line 68,*which is connected with line 65, and thence owsinto a knockout drum 69, in which any entrained liquid material in thegas stream is removed from the bottom thereof through a line 71. Thegaseous product material passes from the top of the knock-out drumbymeans of an overhead line 73, in which there is installed a compressor74, which serves to compress the gaseous material to a pressure of about300 p. s. i. g. and to transport it to recycle 'gas furnace 76 through aline 77. The temperature of the gaseous material at the inlet to thefurnace A76 is 120 F. The gaseous material passes through coil 79 in thefurnace, and then leaves the top thereof through a line 81. The outlettemperature of the gaseous material is 1100 F., which gaseous materialisppass'ed through the furnace at the rate of 84,700 'cubic feet perhour.

The process is operated such that one vessel is being used to hydroformnaphtha, while the other vessel simultaneously is undergoingregeneration to revivify the catalyst. In the description given above,vessel 38 is in the process cycle, consequently, the system is arrangedto permit reactant materials to ow to this vessel, and prevent the ow ofregeneration materials thereto. In View that an excessive quantity ofheat is generated through the regeneration of the catalyst, it isnecessary to employ a cooling means to remove this heat. In thisillustration, the cooling medium employed is a flue gas which isprepared by burning a light naphtha (gaseous fuel can also be readilyused), and then cooling the resltant iue gas prior to introducing thesame into the vessel undergoing regeneration. In this regard, a lightnaphtha is supplied through a source 90, and then b'y means of a pump 91it is passed into a steam heater 93 by means of line 94. The lightnaphtha is supplied at the rate of 35 barrels per day. In the heatexchanger 93, the steam indirectly vaporizes and heats the naphthamaterial to a temperature of 300 F. The heated naphtha vapor is thenpassed into a knock-out drum -95, by means of line 96, which leads fromthe heat exchanger 93. In the knock-out drum the separated entrainedliquid material is removed therefrom through a bottom line l heater 106.

98; whereas the heated light naphtha vapor material passes into aline 99to which there flows air at the rate of 75,000 cubic feet per hour, bymeans of a line 101. The air is supplied from a source 103, and then bymeans of a compressor 104 and line 105 it flows to a steam In the steamheater, the temperature of the air is raised to 300 F., and thereafterit flows into line 101 previously mentioned. The combined streams oflight naphtha vapor and air ow into a flue gas generator 10S wherein thelight naphtha is burned to produce flue gas. The ue gas thus produced isdischarged from the top of the liuc gas generator by means of line 110,and then it passes into the bottom part of a gas cooler 111, wherein itows upwardly in countercurrent contact with a downowing stream of water,which is introduced at the top of the cooler tower by means of a line112. A portion of the ue gas, which is produced in the generator 108,Hows from line into another line 114 which serves to transport thismaterial to the vessel undergoing regeneration. The ue ygas which iscooled in tower 111, flows from the top of the tower by means of anoverhead line 116, and then it is transported by means of a compressor117 and a line 118 to the ue gas generator 108 as recycle. Thetemperature of the recycled flue gas to the gas generator is 86 F. Thewater which is used in the cooling tower 111, for cooling vthe lue gas,is discharged from the bottom thereof by means of a valved line 121 andthen discarded. The temperature of the flue gas used in the regenerationof the catalyst is controlled automatically by controlling the quantityof 'flue gas recirculated through the cooling tower 111.

The air used for the regeneration of catalyst is supplied from a source1 25. This air is transported by means of a compressor y126 through aline 127, which connects to line 114 containing the flue gas, whichserves as heat diluent. The combined streams of flue gas and air pass asa single stream through a conduit 129, and thence, it ows into a line130 which divides in order to provide a ow of regeneration gas to eitherprocessing vessel depending upon the position of valves in the lines inquestion. In this example, line 130 contains a valve 131 which ismaintained in the open position in order that the regeneration gasfio'ws into the top section 134 of processing vessel 135. Whenprocessing vessel 38 is undergoing regeneration, valve 131 is closed,and the regeneration gas iiowing through line 129 is passed through line137 in which there is located a Valve 138. Likewise, the combined feedmaterial and recycle gas may be introduced into processing vessel bymeans of line 141 in which there is installed a valve 142. Similarly,recycle gas for the purging or repressuring functions may be charged toprocessing vessel 135 through a line 144 which is connected to recyclegas line 49 and which contains a valve 145.

The average temperature of regeneration in vessel 135 is maintained at915 F. The ue gas produced through the combustion of carbonaceousmaterial on the catalyst first passes from processing vessel 135 intolower section 147 thereof. The flue gas then passes from the bottom ofsection 147 through a line 148 and a valve 149, and then into the ventline 150, which is connected to the flue gas stack (not shown). There isalso connected to section 147 of processing vessel 135, a line 152containing valve 153, for the purpose of transporting the reactionproduct from section 147 to the recovery system, when this processingvessel is being used on reaction cycle.

The liquid product which is discharged from the gas separator 55 flowsthrough line 60 and then into a heat exchanger 160, wherein thetemperature is raised from 86 F. to 207 F. The liquid product passesthrough line 60 at the rate of 125 barrels per day, and after beingheated in exchanger 160, it passes through a line 161, before enteringinto either feed line 162 or 163 of the stabilizer tower 165. The top ofthe stabilizer tower is maintained at 145 F.; whereas the bottomtemperature is 315 F. The pressure at the top of the stabilizer tower isapproximately 178 p. s. i. The bottom of the tower is maintained at thedesired temperature by withdrawing liquid from a trapout tray 166, andpassing the same through line 167 and into a heater 168, beforereturning to the bottom of the tower through a line 169. The overheadproduct passes from the top of the tower 165 through a line 171, andthen it passes through a condenser 172 prior to entering the accumulator174. Stabilizer gas is removed from the accumulator through an overheadline 175 at the rate of 1940 cubic feet per hour, and this line containsa control valve 177 by means of which the pressure in the stabilizer 165is maintained. The stabilizer gas then passes into a line 178 whichleads to a venting system, not shown. The liquid material in theaccumulator 174 is withdrawn from the bottom thereof through line 180and it is transported by means of a pump 181 and line 182 to the top ofthe stabilizer tower 165 as total reflux, at the rate of 440 barrels perday. The. stabilized liquid product is withdrawn from the bottom of thestabilizer column 165 by means of aline 185, and then it is passedthrough heat exchanger 160 wherein the heat contained by it isindirectly transferred to the incoming unstabilized liquid feed to thetower. From the heat exchanger 160, the stabilized liquid product havinga temperature of 165 F. passes at a rate of 529 barrels per day throughline 186, which later enters at either feed inlet 187 or 188 of thetirst fractionating tower 190. In this tower, the temperature at the topis maintained at 216 F., and at the bottom, the temperature is 358 F.The pressure in this tower is maintained at 40 p. s. i. g. The bottomtemperature is controlled by circulating liquid from the trapout tray192 in the bottom of the tower, through a line 193 which leads to heater194, wherein the temperature is raised to the desired level, before itis returned to the tower by means of line 195. The vapors at the top ofthe tower pass overhead through line 197, in which there is located acontrol valve 198 for the purpose of maintaining the pressure in thesystem. The overhead vapors rst pass into condenser 201, then flowthrough line 202, and nally pass into accumulator 203. Normally gaseousmaterials are discharged from the accumulator by means of line 204, inwhich there is situated Valve 205 for controlling the pressure therein.This discharged gaseous material ilows into line 207, which leads to theventing system previously mentioned and not shown. The liquid product inaccumulator 203 is withdrawn from the bottom thereof through a line 208,and then it is pumped by means of pump 209 into line 210 before dividinginto lines 211 and 212. The liquid in line 211 is refluxed to the top oftower 190 at the rate of 220 barrels per day. The liquid in line 212 owsat the rate of 447 barrels per day, and this stream again divides sothat a portion thereof, namely, 82 barrels per day pass through line 215and the other portion, namely, 365 barrels per day pass through line216, whereby it is transported by means of pump 217 and line 16 and intofeed surge drum 10. The net production of light naphtha which owsthrough line 215 is then passed into a storage tank 218. This line 215contains a control valve 219 for the purpose of controlling the rate ofliquid flow therethrough.

The liquid product is withdrawn from the bottom of tower 190 by means ofline 230 at a temperature of 295 F. This liquid then passes into feedinlets 231, 232 and 233 of the second fractionating tower 235. The toptemperature of the tower is maintained at 286 F.; whereas the bottomtemperature is 380 F. The overhead vapors from tower 235 are rst passedthrough a line 236, then into a condenser 237, and finally flow into anaccumulator 238 by means of a line 239. The pressure in the accumulatoris maintained at 8.5 p. s. i. g., and the temperature of the liquid is93 F. The liquid product is'withdrawn from the bottom of accumulator 238by' means of Aa line 240, and it is passed by means of a pump 241 intoline 242 before dividing into two streams which flow through lines 243and 244. The liquid passing through line 243 is refluxed to the top ofthe tower at the rate of 1040 barrels per day. The net yield of liquidproduct passes through line 244 at the rate of 82 barrels per day, andit ows into storage tank 218 wherein it is mixed with the light naphtha,which was yielded from the overhead of the first fractionating tower190. The overhead product from tower 235 has the following properties:

The nished aviation gasoline product is withdrawn from the storage tank218 by means of a bottom line 250. A heavy naphtha polymer is withdrawnfrom the bottom of tower V235 through a line 251, and then by means ofpump 252 it is passed through a line 253 before dividing into lines 254and 255. The heavy polymer in line 254 is passed through a heater 256wherein its temperature is raised to 216 F. and then it is returned tothe bottom of the tower through a line 258. The heavy polymer in line255 represents the net yield of this material from the system, and it ispassed to a fuel oil system not shown.

Having thus described my invention by reference to specific examplesthereof, it should be understood that no undue limitations orrestrictions are to be imposed by reason thereof, but that the scope ofthis invention is defined by the appended claims.

I claim:

1. A reforming process for producing a 130 grade aviation gasoline whichcomprises contacting a naphtha having about 20 to about 60% naphtheneswith a catalyst Selected from the group consisting of molybdenum oxide,chromium oxide, and platinum metal at a temperature of about 850 to 1050F., a pressure of about 25 to about 1000 p. s. i. g., in the presence ofhydrogen supplied at the rate of about 500 to about 20,000 SCFB, at aweight space velocity of about 0.10 to about 4.0, thus producing areaction product including aromatics and acyclic hydrocarbons having 5and 6 carbon atoms, separating a Cs-Cs fraction from the reactionproduct, recycling a portion of the Ces-C6 fraction at a recycle ratioof about 0.5 to about 3.0:1 for further contact with the catalyst,separating an aromatic fraction having a boiling point of about 180 toabout 225 F. and an end point of about 280 to about 325 F. from theremainder of the reaction product, and combining the remainder of theCs-Cs fraction and the aromatic fraction as the product of the process.

2. A reforming process for producing a 100/ 130 grade aviation gasolinewhich comprises contacting a naphtha having about 20 to about 60%naphthenes withra molybdenum oxide catalyst, at a temperature of about850 to about 1050 F., a pressure of about 25 to about 1000 p. s. i. g.,in the presence of hydrogen supplied at the rate of about 500 to about20,000 SCFB, at a weight space velocity of about 0.10 to about 4.0, thusproducing a reaction product including aromatics and acyclichydrocarbons having 5 and 6 carbon atoms, separating a Cta-Cs fractionfrom the reaction product, recycling a portion of the Cs-Ce fraction ata recycle ratio of about 0.5 to

about 3.0:1 for further contact with the molybdenum oxide catalyst,`separating an aromatic fraction having an initial boiling point ofabout 180 to about 225 F. and an end point of about 280 to about 325 F.from 'the remainder of the reaction product, and combining the remainderof the Csi-C fraction and the aromatic fraction as the product of theprocess.

3. A reforming process for producing a 100/ 130 grade aviation gasolinewhich comprises contacting a naphtha having about to about 60%naphthenes with a molybdenum oxide 'catalyst in a reforming zone, at atemperature of about 900 to about 975 F., a pressure of about to about500 p. s. i. g., in the presence of hydrogen which is -supplied to thereforming zone at the rate of about 1500 to about 7500 SCFB, at a Weightspace velocity of about 0.1 to about 1.0, thus producing a reactionproduct including aromatics and acyclic hydrocarbons having 5 and 6carbon atoms, separating a C5-Cs fraction from the reaction product,recycling a portion of the Cs-Cs fraction to the reforming zone at arecycle ratio or". about 0.5 to about 3.0: 1, separating an aromaticfraction having an initial boiling point of about 180 to 225 F. and anend point of about 280 to about 325 F. from the remainder of thereaction product, and combining the remainder of the Cs-Ce fraction andthe aromatic fraction as the product of the process.

4. A reforming process for producing a /130 grade aviation gasolinewhich comprises contacting a naphtha having about 20 to about 60%naphthenes with a uidized mass of molybdenum oxide catalyst in thereforming zone,

12 at a temperature of about 900 to about 975 F., a pressure of about 50to about 500 p. s. i. g., in the presence of hydrogen which is suppliedto the reforming zone at the rate of about 1500 to about 7500 SCFB, at aweight space velocity of about 0.1 to about 1.0, tnus producing areaction product including aromatics and acyclic hydrocarbons having 5and 6 carbon atoms, separating a Cs-Cs fraction from the reactionproduct, recycling a portion of the Cs-Ce fraction to the reforming zoneat a recycle ratio ofV 0.5 to 30:1, separating an aromatic fractionhaving an initial boiling point of about 180 to about 225 F. and an endpoint of about 280 to about 325 F. from the remainder of the reactionproduct, and combining the remainder of the C5-C fraction and thearomatic fraction as the product of the process.

References Cited in the tile of this patent UNITED STATES PATENTS2,361,138 Voorhies et al. Oct. 24, 1944 2,364,453 Layng et al. Y Dec. 5,1944 2,406,117 Welty Aug. 20, 1946 2,635,123 Kennedy Apr. 14, 1953 OTHERREFERENCES 30, December

1. A REFORMING PROCESS FOR PRODUCING A 100/130 GRADE AVIATION GASOLINEWHICH COMPRISES CONTACTING A NAPHTHA HAVING ABOUT 20 TO ABOUT 60%NAPHTHENES WITH A CATALYST SELECTED FROM THE GROUP CONSISTING OFMOLYBDENUM OXIDE, CHROMIUM OXIDE, AND PLATINUM METAL AT A TEMPERATURE OFABOUT 850 TO 1050* F., A PRESSURE OF ABOUT 25 TO ABOUT 1000 P. S. I. G.,IN THE PRESENCE OF HYDROGEN SUPPLIED AT THE RATE OF ABOUT 500 TO ABOUT20,000 SCFB, AT A WEIGHT SPACE VELOCITY OF ABOUT 0.10 TO ABOUT 4.0, THUSPRODUCING A REACTION PRODUCT INCLUDING AROMATICS, AND ACYCLICHYDORCARBONS HAVING 5 AND 6 CARBON ATOMS, SEPARATING A C5-C6 FRACTIONFROM THE REACTION PRODUCT, RECYCLING A PORTION OF THE C5-C6 FRACTION ATA RECYCLE RATIO OF ABOUT 0.5 TO ABOUT 3.0:1 FOR FURTHER CONTACT WITH THECATALYST, SEPARATING AN AROMATIC FRACTION HAVING A BOILING POINT OFABOUT 180* TO ABOUT 225* F. AND AN END POINT OF ABOUT 280* TO ABOUT 325*F. FROM THE REMAINDER OF THE REACTION PRODUCT, AND COMBINING THEREMAINDER OF THE C5-C6 FRACTION AND THE AROMATIC FRACTION AS THE PRODUCTOF THE PROCESS.